1. Field of the Invention
This invention relates to novel nanoparticles comprised of a protein-poly(aliphatic-cyanoacrylate) copolymer and a process for their production. The nanoparticles may be used as a surface treatment to alter the wetting properties of a variety of different materials.
2. Description of the Prior Art
Alkyl-2-cyanoacrylates, usually the products of condensation of formaldehyde with cyanoacetate, are low viscosity liquids with excellent wetting properties. Alkyl-2-cyanoacrylates undergo spontaneous anionic polymerization to form poly(alkyl-cyanoacrylate) (PACA) a degradable polymer. The polymerization occurs at room temperature and is initiated by anionic active species, such as weak bases including moisture and alcohol, amines, phosphines, and alkaline materials, due to the unique electron withdrawing properties of nitrile and carboxylate groups substituted on carbon 2. In addition to the ability to polymerize rapidly (at room temperature in absence of a catalyst) and good wetting properties, the high polarity and high bond strength between various adherents make the properties of the alky-2-cyanoacrylate unique. As a result, the alkyl-2-cyanoacrylates have wide range of applications, including instantaneous adhesives for rubbers, plastics, metals, glass and the like, and are commonly known as “super glue.” Alkyl-2-cyanoacrylates also have been used as tissue adhesives for the treatment of skin wounds and as surgical glues due to their bonding properties with most polar substrates, including living tissues and skin and biocompatible properties. Recently, PACA has been used as polymer colloidal drug delivery systems, especially for treatment of cancers and intracellular infections.
Although alkyl-2-cyanoacrylates are commonly polymerized by anionic polymerization, they also can be prepared by free radical polymerization methods. The resulting poly(alkyl-2-cyanoacrylates) are basically hard, colorless, and amorphous polymers. Physical properties of these polymers are variable, dependent on the size of the alkyl substituent, molecular weight, polymerization conditions and methods, and contaminants. However, the use of cyanoacrylate polymer as conventional plastic materials has been seldom studied. This may be due to the fact that retropolymerization reaction or degradation at elevated temperatures restricts the use of this polymer where the prolonged service temperature is below 100° C. Furthermore, there is no report on polymer composites using cyanoacrylate, although its fast, easy polymerization and relatively good mechanical properties should allow for facile production of polymer composites (see Kung et al., Macromolecules, 33:8192-8199, 2000).
Alkyl cyanoacrylate is a major component of a well-known adhesive, “super glue”, that was introduced in the early 1970s. The preparation of alkyl cyanoacrylate esters was first reported by scientists at B. F. Goodrich in 1949, and these monomers were observed to produce hard, glassy polymers after thermal polymerization (Ardis, 1949, U.S. Pat. No. 2,467,926). Alkyl cyanoacrylate esters could effectively perform as one-part liquid adhesives, which would cure rapidly at room temperature. Unlike epoxy or acrylic adhesives, alkyl cyanoacrylate adhesives polymerize, in many cases, without the need for an added initiator or curing agent. The first cyanoacrylate instant adhesive, Eastman 910, which utilized methyl cyanoacrylate as the monomer, was marketed in 1958. Because of the ability of the cyanoacrylates to bond to a wide variety of substrates, cyanoacrylate instant adhesives are now produced in multi-ton quantities for both industrial and consumer applications.